This invention relates to electrical devices and their use, and, more particularly, to electrical devices which are self-compensated as to temperature.
Electrical devices contain two or more interconnected circuit elements. The performance of most circuit elements degrades with increasing temperature. Examples of this degradation include resistors, whose resistance generally decreases with increasing temperature; capacitors, whose capacitance decreases with increasing temperature; and silicon transistors, whose gain decreases with increasing temperature.
There are well established examples of the undesirable effects of temperature on circuit performance. Once example is amplifiers, which lose bandwidth as the temperature is increased. Another example is active filters, which exhibit shifts in pass-band as the temperature changes.
The changes in performance with temperature in most circuit elements is due largely to the inherent properties of the materials used to manufacture the circuit elements. Materials used in capacitor dielectrics exhibit decreases in permittivity with increases in temperature. Transistors exhibit lower gain at higher temperatures due to reduced carrier mobility in the semiconductor material from which they are made. As a result, it is not possible to compensate the performance variance with temperature with changes in the design of the circuit elements. Compensation for temperature changes may be possible with changes in the circuit design, or with the addition of circuitry to detect the temperature and compensate for temperature-based changes in material properties. These additions or modifications are not possible in all cases, and, even where possible, may not be desirable due to other factors such as increased cost, reduced reliability, or adverse effects on other aspects of the performance of the circuit.
There is a need for an improved approach to minimizing or avoiding the adverse consequences of the temperature variance of material properties on the performance of electrical devices. The present invention fulfills this need, and further provides related advantages.